长期施用化肥和稻草对红壤性水稻土非交换性钾释放动力学的影响

研究了长期定位施肥试验中连续27年(1981-2007)施用化肥和稻草对红壤性水稻土非交换性钾释放特征及其动力学的影响.本试验选择了其中5个处理:CK(不施肥)、NP(施氮、磷肥)、NPK(施氮、磷、钾肥)、NP+RS(施氮、磷肥和稻草)和NPK+RS(施氮、磷、钾肥和稻草).结果表明,长期施用钾肥和稻草的条件下,各处理土壤中非交换性钾的释放均存在2个不同的阶段:即第一阶段(1～14 h)表现为直线上升阶段,第二阶段(14～796 h)为缓慢增长阶段.5个处理中,长期不施钾处理(CK和NP)的土壤非交换性钾累积释放量较低,分别为62.22和56.12 mg/kg,长期施钾处理(NPK、NP+RS和NPK+RS)的土壤非交换性钾累积释放量较高,分别为67.52、64.41和75.33 mg/kg.施稻草处理(NPK+RS和NP+RS)的土壤非交换性钾释放量明显高于相应不施稻草处理(NPK和NP)的土壤,这可能与长期施用稻草促使土壤矿物钾中的一部分向非交换性钾转化有关.用抛物线扩散、零级反应、一级反应和Elovich方程模拟土壤非交换性钾的释放动力学结果表明,Elovich方程能比较好地模拟5个处理土壤非交换性钾的释放动力学.分段直线方程能更好地描述土壤非交换性钾释放的机制.

Effects of long-term application of fertilizer and rice straw on release kinetics of non-exchangeable potassium in reddish paddy soil

A 27 years of long-term experiment was conducted to evaluate the effects of fertilizer and rice straw application on release characteristics of non-exchangeable potassium (K) and its release kinetics in reddish paddy soil. There were 5 treatments in study, namely: CK (without fertilization), NP (N, P fertilizers), NPK (N, P and K fertilizers), NP+RS (NP plus rice straw) and NPK+RS (NPK plus rice straw). The results showed that there were two different phases in change of non-exchangeable K release of each treatment, i. e., the linear increase in the first phase (1-14 h) and slow increase in the second phase (14-796 h). The accumulations of non-exchangeable K release in the long-term K fertilization (NPK, NP+RS and NPK+RS) treatments were higher than those in treatments where no K fertilizer was applied (CK and NP). The accumulations of non-exchangeable K release were 62.22 mg/kg and 56.12 mg/kg in the treatments where no K fertilizer was applied (CK and NP), while 67.52, 64.41 and 75.33 mg/kg in treatments where K fertilizer were applied (NPK, NP+RS and NPK+RS), respectively. The accumulations of non-exchangeable K release in the treatments with rice straw application (NP+RS and NPK+RS) were significantly higher than those with no application of rice straw (NP and NPK), which may promote the change from the part of soil mineral potassium to non-exchangeable K under long-term application of rice straw. The four kinds of kinetic equations (parabolic diffusion equation, zero-order equation, first-order equation and Elovich equation) were tested for their suitability to describe the release of non-exchangeable K from the five different treatments. The kinetics of non-exchangeable K release for five treatments could better be simulated by Elovich equation. The segmented straight line equation established from two different phases can better explain the mechanism of release kinetics of non-exchangeable in reddish paddy soil.